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Carbon Nanotubes Carbon nanotubes (CNTs) are allotropes of carbon with a nanostructure that can have a length-to-diameter ratio greater than 10,000,000 and as high as 40,000,000 as of 2004. These cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential uses in architectural fields. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs. The cylindrical nanotube usually has at least one end capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is in the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to several millimeters in length (as of 2008). Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). The nature of the bonding of a nanotube is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than the sp3 bonds found in diamonds, provides the molecules with their unique strength. Nanotubes naturally align themselves into ''ropes'' held together by Van der Waals forces. Under high pressure, nanotubes can merge together, trading some sp² bonds for sp³ bonds, giving the possibility of producing strong, unlimited-length wires through high-pressure nanotube linking. The strength and flexibility of carbon nanotubes makes them of potential use in controlling other nanoscale structures, which suggests they will have an important role in nanotechnology engineering. The highest tensile strength an individual multi-walled carbon nanotube has been tested to be is 63 GPa. A 2006 study published in Nature determined that some carbon nanotubes are present in Damascus steel, possibly helping to account for the legendary strength of the (almost ancient) swords made of it. Structural: Because of the great mechanical properties of the carbon nanotubule, a variety of structures have been proposed ranging from everyday items like clothes and sports gear to combat jackets and space elevators. However, the space elevator will require further efforts in refining carbon nanotube technology, as the practical tensile strength of carbon nanotubes can still be greatly improved. For perspective, outstanding breakthroughs have already been made. Pioneering work led by Ray H. Baughman has shown that single and multi-walled nanotubes can produce materials with toughness unmatched in the man-made and natural worlds. Recent research by James D. Iverson and Brad C. Edwards has revealed the possibility of cross-linking CNT molecules prior to incorporation in a polymer matrix to form a super high strength composite material. This CNT composite could have a tensile strength on the order of 20 million psi (138 GPa, for 106 MN•m•kg1), potentially revolutionizing many aspects of engineering design where low weight and high strength is required. In electrical circuits: Carbon nanotubes have many properties—from their unique dimensions to an unusual current conduction mechanism—that make them ideal components of electrical circuits. For example, they have shown to exhibit strong electron-phonon resonances, which indicate that under certain direct current (dc) bias and doping conditions their current and the average electron velocity, as well as the electron concentration on the tube oscillate at terahertz frequencies. These resonances can be used to make terahertz sources or sensors. Nanotube based transistors have been made that operate at room temperature and that are capable of digital switching using a single electron. One major obstacle to realization of nanotubes has been the lack of technology for mass production. However, in 2001 IBM researchers demonstrated how nanotube transistors can be grown in bulk, not very differently from silicon transistors. The process they used is called ''constructive destruction'' which includes the automatic destruction of defective nanotubes on the wafer. This has since then been developed further and single-chip wafers with over ten billion correctly aligned nanotube junctions have been created. In addition it has been demonstrated that incorrectly aligned nanotubes can be removed automatically using standard photolithography equipment. The first nanotube integrated memory circuit was made in 2004. One of the main challenges has been regulating the conductivity of nanotubes. Depending on subtle surface features a nanotube may act as a plain conductor or as a semiconductor. A fully automated method has however been developed to remove non-semiconductor tubes. An alternative way to make transistors out of carbon nanotubes has been to use random networks of them. By doing so one averages all of their electrical differences and one can produce devices in large scale at the wafer level. This approach enabled making the first transistor on a flexible and transparent substrate. As a vessel for drug delivery: The nanotube’s versatile structure allows it to be used for a variety of tasks in and around the body. Although often seen especially in cancer related incidents, the carbon nanotube is often used as a vessel for transporting drugs into the body. The nanotube allows for the drug dosage to hopefully be lowered by localizing its distribution, as well as significantly cut costs to pharmaceutical companies and their consumers. The nanotube commonly carries the drug one of two ways: the drug can be attached to the side or trailed behind, or the drug can actually be placed inside the nanotube. Both of these methods are effective for the delivery and distribution of drugs inside of the body. Current applications They are used as bulk nanotubes, which is a mass of rather unorganized fragments of nanotubes. Bulk nanotube materials may never achieve a tensile strength similar to that of individual tubes, but such composites may nevertheless yield strengths sufficient for many applications. Bulk carbon nanotubes have already been used as composite fibers in polymers to improve the mechanical, thermal and electrical properties of the bulk product. CNT technology has been used by a bike company in a number of their components - including flat and riser handlebars, cranks, forks, seatposts, stems and aero bars. Solar cells A solar cell developed uses a carbon nanotubes complex, formed by carbon nanotubes and combines them with tiny carbon buckyballs (known as fullerenes) to form snake-like structures. Buckyballs trap electrons, although they can't make electrons flow. Add sunlight to excite the polymers, and the buckyballs will grab the electrons. Nanotubes, behaving like copper wires, will then be able to make the electrons or current flow. Ultracapacitors One laboratory for Elecromagnetic and Electronic Systems uses nanotubes to improve ultracapacitors. The activated charcoal used in conventional ultracapacitors has many small hollow spaces with a distribution of sizes, which create together a large surface to store electric charges. But as charge is quantized into elementary charges, i.e. electrons, and each of these needs a minimum space, a large fraction of the electrode surface is not available for storage because the hollow spaces are too small. With an electrode made out of nanotubes, the spaces are hoped to be tailored to size - few too large or too small - and consequently the capacity is hoped to be increased considerably. Other applications Carbon nanotubes have also been implemented in nanoelectromechanical systems, including mechanical memory elements (NRAM) and nanoscale electric motors (Nanomotor). Carbon nanotubes have also been proposed as a possible gene delivery vehicle and for use in combination with radiofrequency fields to destroy cancer cells. One company was able to put on the market an electronic device that integrated carbon nanotubes on a silicon platform, in May 2005. It was a Hydrogen sensor. Since then they have been patenting many such sensor applications such as in the field of carbon dioxide, nitrous oxide, glucose, DNA detection etc... Others are developing transparent, electrically conductive films of carbon nanotubes to replace indium tin oxide (ITO). Carbon nanotube films are substantially more mechanically robust than ITO films, making them ideal for high reliability touch screens and flexible displays. Printable water-based inks of carbon nanotubes are desired to enable the production of these films to replace ITO. Nanotube films show promise for use in displays for computers, cell phones, PDAs, and ATMs. A nanoradio, a radio receiver consisting of a single nanotube, was demonstrated in 2007. In 2008 it was shown that a sheet of nanotubes can operate as a loudspeaker if an alternating current is applied. The sound is not produced through vibration but thermoacoustically. Carbon nanotubes are said to have the strength of diamond, and research is being made into weaving them into clothes to create stab-proof and bulletproof clothing. The nanotubes would effectively stop the bullet from penetrating the body but the force and velocity of the bullet would be likely to cause broken bones and internal bleeding. A flywheel made of carbon nanotubes could be spun at extremely high velocity on a floating magnetic axis, and potentially store energy at a density approaching that of conventional fossil fuels. Since energy can be added to and removed from flywheels very efficiently in the form of electricity, this might offer a way of storing electricity, making the electrical grid more efficient and variable power suppliers (like wind turbines) more useful in meeting energy needs. The practicality of this depends heavily upon the cost of making massive, unbroken nanotube structures, and their failure rate under stress. Rheological properties can also be shown very effectively by carbon nanotubes. If you can think of an application for such nanotubes useful for your business, let us know and receive our input. We can design, prototype, manufacture, test and deliver these to you from advanced fabs specialized in such applications. We are also experts in intellectual property protection and can make special arrangements for you to ensure your designs and products are not copied. Our nanoparticle designers are some of the best in the World with multiple patents each, royalty rights for their inventions, dozens of engineering publications and Ph.D degrees from institutions such as Stanford University, UCSD, Berkley, Massachussets Institute of Technology, Yale University, Caltech, Princeton, Bell Laboratories. They are the people who developed some of the World's most advanced materials and devices. Contact AGS-TECH Inc. for details of capabilities. Do you need design assistance ? Do you need prototypes ? Do you need mass manufacturing ? We are here to help you. If you are mostly interested in our engineering and research & development capabilities instead of manufacturing capabilities, then we invite you to visit our sister website http://www.ags-engineering.com |
